Preliminary results of a phase I trial of FT516, an off-the-shelf natural killer (NK) cell therapy derived from a clonal master induced pluripotent stem cell (iPSC) line expressing high-affinity, non-cleavable CD16 (hnCD16), in patients (pts) with relapsed/refractory (R/R) B-cell lymphoma (BCL)

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Background: FT516 is an investigational, NK cell cancer immunotherapy derived from a clonal master iPSC line. FT516 is engineered with a novel hnCD16 Fc receptor, demonstrated preclinically to maximize antibody-dependent cellular cytotoxicity (Zhu et al. Blood 2020). FT516 can be mass produced and made available off-the-shelf for broad pt access and multi-dose administration. Methods: This is a Phase I trial of FT516 combined with rituximab (R) in pts with R/R BCL. Treatment consists of 2 cycles, each with 3 days lympho-conditioning (fludarabine 30 mg/m2 and cyclophosphamide 500 mg/m2) and 1 dose of R followed by 3 weekly infusions of FT516 (planned doses 30-900 million/dose) with IL-2 (6 MIU after each FT516 dose). The primary objective is to identify the incidence of dose-limiting toxicity (DLT)/dose cohort and the recommended Phase II dose using a standard 3+3 design. Additional objectives include safety, tolerability, preliminary activity, pharmacokinetics, and immunogenicity. Results: Six pts (5 DLBCL, 1 FL, median age 65.5 y) have completed (5) or discontinued (1) study treatment after the DLT period (data cutoff 9 Dec 2020): 2 received 30 million cells/dose, 3 received 90 million cells/dose, and 1 received 300 million cells/dose. All pts received > 1 prior R-containing regimen, and median number of prior therapies was 3 (range 2-6), including CAR-T in 3 pts. FT516 was primarily administered in the outpatient setting. No FT516-related Grade ≥3 adverse events (AEs) or serious AEs, and no events of cytokine release syndrome (CRS), immune effector cell-associated neurotoxicity syndrome (ICANS), or graft-versus-host disease (GvHD) of any grade were reported. DLT (Grade 4 neutrophil count decreased, not recovered to baseline by D29) was reported in the first pt at 30 million cells/dose and R dosing of 375 mg/m2 weekly x 4/cycle, resulting in modification of R dosing to once/cycle; no DLTs were observed with modified R dosing. Most common all grade AEs in ≥3 pts: fatigue (4 pts) and decreased appetite, nausea, neutrophil count decreased, and headache (3 pts each). Grade ≥3 AEs in ≥2 pts: neutrophil count decreased (3 pts) and febrile neutropenia and platelet count decreased (2 pts each); none considered related to FT516. Host anti-product B- or T-cell immunogenicity was not observed. Three of 4 pts treated at ≥90 million cells/dose achieved objective response (2 complete responses [CRs] and 1 partial response). Conclusions: Administration of up to 6 doses of FT516 cells, including up to 300 million cells/dose, appears to be safe and tolerable, without CRS, ICANS, or GvHD. Activity was observed, including CRs, in heavily pretreated pts. Dose escalation is ongoing. Updated clinical and translational data will be presented. Clinical trial information: NCT04023071.

Three-year follow-up of treatment-naïve and previously treated patients with Waldenström macroglobulinemia (WM) receiving single-agent zanubrutinib

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Background: Inhibitors of Bruton tyrosine kinase (BTK) have established therapeutic activity in patients with WM. Zanubrutinib, a potent and selective BTK inhibitor was evaluated in a phase 1/2 study in treatment-naïve (TN) and relapsed/refractory (R/R) patients with WM. Methods: Patients had TN or R/R WM and required treatment as per International Workshop on WM (IWWM) criteria. Treatment consisted of oral zanubrutinib at 160 mg twice daily (n = 50) or 320 mg once daily (n = 23) until disease progression or unacceptable toxicity. Efficacy endpoints included the proportion of patients achieving a complete response (CR) or very good partial response (VGPR) in accordance with IWWM-6 criteria. Efficacy analyses were conducted on the 73 patients evaluable (24 TN, 49 R/R). Results: Between September 2014 and August 2018, 77 patients with WM (24 TN and 53 R/R) began treatment with zanubrutinib (55% aged > 65 years; 21% aged > 75 years). At a median follow up of 32.7 months, 73% remain on treatment. Reasons for treatment discontinuation included adverse events (AE) in 13% (only one related), disease progression (10.4%), and other (3.9%). Results are presented for TN and R/R combined. The overall response rate was 96% and VGPR/CR rate was 45%. The rates of VGPR/CR increased over time; 22% at 6 mos, 33% at 12 months and 45% at 24 months. Three-year progression-free survival (PFS) was 81%, and overall survival (OS) was 85%. The most commonly reported AEs were upper respiratory tract infection (52%), contusion (33%, all grade 1) and cough (22%). AEs of interest include neutropenia (18.2%), major hemorrhage (4%), atrial fibrillation/flutter (5%), and grade 3 diarrhea (3%). Conclusions: Long-term follow up with continued zanubrutinib treatment demonstrated deep and durable responses in the majority of WM patients. The rates of VGPR/CR increased with prolonged therapy. Disease progression was uncommon. The safety profile of long-term zanubrutinib therapy in these patients was tolerable. Clinical trial information: NCT02343120 . [Table: see text]

Molecular biomarker analyses using circulating tumor cells

Background: Evaluation of cancer biomarkers from blood and other accessible tissues could significantly enable biomarker assessment by providing a relatively noninvasive source of representative tumor material. Circulating tumor cells (CTCs) isolated from blood of metastatic cancer patients hold significant promise in this regard.

Methodology/Principal Findings: Using a tumor-cell spike-in model system we evaluated CTC capture on different CTC technology platforms, including CellSearch® and two biochip platforms, and used the isolated CTCs to develop and optimize assays for molecular characterization of CTCs. We report similar performance for the various platforms tested in capturing CTCs, and find that capture efficiency is dependent on the level of EpCAM expression. We demonstrate that captured CTCs are amenable to biomarker analyses such as HER2 status, qRT-PCR for breast cancer subtype markers, KRAS mutation detection, and EGFR staining by immunofluorescence (IF). We demonstrate that cell surface expression of EGFR can be quantitated in CTCs from metastatic lung cancer patient samples. In addition, we determined HER2 status by IF and FISH in CTCs from metastatic breast cancer patients and in the majority of patients (89%) found concordance with HER2 status from patient tumor tissue, while in a subset of patients (11%), HER2 status had changed from the primary tumor at diagnosis. Surprisingly, we found CTC counts to be higher in ER+ patients in comparison to HER2+ and triple negative patients despite their more aggressive phenotype. This may be explained by our findings that the basal-like molecular subtype of breast cancer has low EpCAM expression and a more mesenchymal phenotype and CTCs will likely not be efficiently captured using EpCAM alone in tumors that arise from this subtype.

Conclusions/Significance: Our data suggests that molecular characterization from captured CTCs is possible and can inform us of the patients’ current biomarker status. In this regard, CTCs hold significant promise as a source of tumor material to facilitate clinical biomarker evaluation. However, limitations exist from a purely EpCAM-based capture system and addition of antibodies to mesenchymal markers in addition to EpCAM could further improve CTC capture efficiency to enable routine biomarker analysis from CTCs.

Molecular biomarker analyses using circulating tumor cells

Background

Evaluation of cancer biomarkers from blood could significantly enable biomarker assessment by providing a relatively non-invasive source of representative tumor material. Circulating Tumor Cells (CTCs) isolated from blood of metastatic cancer patients hold significant promise in this regard.

Methodology/Principal Findings

Using spiked tumor-cells we evaluated CTC capture on different CTC technology platforms, including CellSearch® and two biochip platforms, and used the isolated CTCs to develop and optimize assays for molecular characterization of CTCs. We report similar performance for the various platforms tested in capturing CTCs, and find that capture efficiency is dependent on the level of EpCAM expression. We demonstrate that captured CTCs are amenable to biomarker analyses such as HER2 status, qRT-PCR for breast cancer subtype markers, KRAS mutation detection, and EGFR staining by immunofluorescence (IF). We quantify cell surface expression of EGFR in metastatic lung cancer patient samples. In addition, we determined HER2 status by IF and FISH in CTCs from metastatic breast cancer patients. In the majority of patients (89%) we found concordance with HER2 status from patient tumor tissue, though in a subset of patients (11%), HER2 status in CTCs differed from that observed in the primary tumor. Surprisingly, we found CTC counts to be higher in ER+ patients in comparison to HER2+ and triple negative patients, which could be explained by low EpCAM expression and a more mesenchymal phenotype of tumors belonging to the basal-like molecular subtype of breast cancer.

Conclusions/Significance

Our data suggests that molecular characterization from captured CTCs is possible and can potentially provide real-time information on biomarker status. In this regard, CTCs hold significant promise as a source of tumor material to facilitate clinical biomarker evaluation. However, limitations exist from a purely EpCAM based capture system and addition of antibodies to mesenchymal markers could further improve CTC capture efficiency to enable routine biomarker analysis from CTCs.

Abstract 5768: Predictive diagnostics from circulating tumor cells

Introduction: Tumor tissue collection is essential for biomarker assessment but can be difficult in tumor types such as non small-cell lung cancer (NSCLC) where often no surgery is performed and diagnosis is done with biopsies yielding only very limited tissue quantities. Also, in cases where primary tissue is available, the samples may not be representative of patient's current disease, i.e. in the case of hormone refractory prostate cancer (HRPC).

Rationale: Evaluation of cancer biomarkers (both predictive and pharmacodynamic) from blood and other biological material could significantly enable our ability to generate biomarkers by providing an accessible and relevant source of samples that can be analyzed. Successful assessment of biomarkers that do not require access to tumor “tissue” could improve the inclusion of biomarker evaluations in clinical development and across our oncology practice.

Results: We report on our efforts to evaluate Circulating Tumor Cells (CTC) for utility in tumor biomarker assessment. These efforts included evaluating multiple technologies for isolation and molecular analysis of CTCs from blood. By spiking tumor cells into blood as a model system for CTCs we have developed assays for biomarker evaluation in CTCs including: Fluorescence in situ hybridization (FISH), Immunofluoresecnce (IF), qRT-PCR and mutation detection. Validation of these assays in patient blood is ongoing and early data suggests that biomarker assessment is indeed possible from CTCs. Using blood samples from metastatic, HER2+ breast cancer patients; we were able to evaluate the HER2 status from CTCs using immunofluorescence and/or FISH.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 5768.